Rotary carburetors may include a rotary throttle valve adapted to control a quantity of air flowing through a mixing passage by rotating about an axis and to adjust a quantity of fuel flowing into the mixing passage by shifting in an axial direction and in dependence on the angular position of the rotary throttle valve. Generally, as air flow increases so does fuel flow thus maintaining a substantially constant fuel-and-air ratio of the mixture flowing from the mixing passage and to a warm and running combustion engine. For starting a cold engine, rotary carburetors are known to have starting systems that interact with the rotary throttle valve to generally move the throttle valve axially without rotation, thus increasing the quantity of fuel flowing into the mixing passage without increasing the quantity of air. The result is a richer mixture of fuel-and-air to facilitate cold engine starts.
Typical starting systems for rotary carburetors have a generally planar or plate-like operating member supported slidably by a main body of the rotary carburetor for reciprocal movement to engage a rotating throttle lever of the rotary throttle valve when a richer mixture of fuel-and-air is desired for cold engine starts. A free end or peripheral edge of the operating member typically has a wedge-shaped cam for contacting the throttle lever and moving it in an axial outward direction thus increasing the quantity of fuel flowing into the mixing passage. The operating member of the starting system has only two positions, the rest or disengaged position and the active or engaged position. Therefore, known starting systems are not responsive to varying cold temperatures that ideally require varying degrees of fuel enrichment when starting an engine at different temperatures.